This invention is concerned with methods of controlling and controllers for controlling the operation of a plurality of pusher mechanisms each of which is associated with one of the sections of a glassware forming machine of the individual section type.
Glassware forming machines of the individual section type are well known and comprise a plurality of individual glassware forming sections arranged side-by-side. The sections of the machine receive gobs of molten glass from a common source in turn according to a predetermined sequence. Each section moulds the gobs it receives into pieces of glassware and deposits them on a deadplate associated with the section. The sections operate within an overall machine cycle with phase differences between their operations, the overall machine cycle being the period between successive deliveries of gobs to the same section. For a six section machine, if the machine cycle is represented by 360 degrees, the phase difference between one section and the next section in the predetermined sequence will be 60 degrees. A section may form one, two, three or even four pieces of ware simultaneously from a like number of gobs supplied simultaneously thereto. The basic principle of the individual section, or I.S., machine is described in U.S. patent specification No. 1911119.
The ware formed by an I.S. machine is transported away from the machine on a conveyor which is common to all the sections and runs parallel to the row of sections past the deadplates. In order to transfer ware formed by the sections from the deadplate on to the conveyor, pusher mechanisms are arranged alongside the conveyor adjacent the deadplate. Each pusher mechanism is associated with one of the sections and is operable, once in each cycle of the machine, to transfer ware formed by its associated section on to the conveyor from the deadplate on which the section has deposited the ware. The pusher mechanisms operate successively in a predetermined sequence which is normally the same sequence as that in which the sections are operated.
Each pusher mechanism normally comprises one or more fingers, one for each piece of ware formed simultaneously by its associated section, which in the operation of the mechanism are brought into contact with ware on the deadplate, are moved arcuately to sweep the ware on to the conveyor, and are then retracted from the ware. An example of such a pusher mechanism is described in U.S. patent specification No. 3249200.
The speed of the conveyor needs to be synchronised with the operation of the pusher mechanisms to ensure that all the ware can be transferred to the conveyor without interference with ware already on the conveyor. Furthermore, it is desirable for the subsequent handling of the ware, if the ware on the conveyor is evenly spaced. In order to achieve this synchronisation, conventionally, the conveyor drives a cam shaft on which cams associated with each pusher mechanism are mounted. The cam associated with a particular pusher mechanism starts the operation of its associated pusher mechanism by operating a pneumatic valve to admit operating air to the mechanism. In this arrangement, however, the relative timings of the pusher mechanisms cannot be easily adjusted to take account of variations in the speed of operation of the pusher mechanism which may develop over a period of time. More recently, see e.g. U.S. patent specification No. 4203752 and European patent specification No. 0048133, the pusher mechanisms have been started by electrical control signals derived from the machine controller but, while these can more easily be adjusted, the need for adjustment and the amount of adjustment required depends on observation by an operator and trial-and-error.
It is an object of the present invention to provide a method of controlling the operation of pusher mechanisms of the type referred to in which the timing of the control signals is automatically adjusted to equalise the spacing of ware on the conveyor.